At least 24 people have been killed in a suicide bombing by a Shi'ite mosque in Baghdad.

And 52 others were injured in the blast - the latest in a coordinated string of attacks on the country.

The first bomber detonated his explosives at a security checkpoint near the mosque in the middle-class, Shi'ite-majority area of the northern Qahira neighbourhood in an apparent attempt to distract the authorities, two police officers said.

Amid the commotion, a second bomber slipped into the mosque and blew himself up while worshippers were attending midday prayers, according to police.

A medic in a nearby hospital confirmed the casualties.

There was no immediate claim of who was responsible for the killings, but suicide bombings and attacks against Shi'ite worshippers are frequently the work of al Qaeda's Iraq arm.

The bombing has revived fears that the country is heading back toward the widespread sectarian bloodshed that pushed it to the brink of civil war in 2006 and 2007.

Violence has surged in Iraq in recent months, along with sectarian and political tensions. Insurgents frequently attack Shi'ites considered by Sunni extremists as infidels and non-Muslims.

The bloodshed in Iraq has risen to levels not seen since 2008. Nearly 2,000 people have been killed since the start of April, including more than 220 this month.

On Sunday, a wave of apparently coordinated bombings and a shooting killed at least 51 people.

Fifteen people were killed in bomb attacks on Monday, including one caused by a suicide bomber who set off his explosives-laden belt among a group of policemen in Fallujah, west of Baghdad.